Pages 87-92

advertisement
Pages 87-92
Epithelial Tissues
 Locations:
 Body coverings
 Body linings
 Glandular tissue
 Functions:
 Protection
 Absorption
 Filtration
 Secretion
© 2015 Pearson Education, Inc.
Epithelium Characteristics
 Cells fit closely together and often form sheets
 The apical surface is the free surface of the tissue
 The unattached surface

Can be exposed to exterior or cavity of an organ
 The lower surface of the epithelium (the basal lamina)
rests on a basement membrane
 Consists of reticular connective tissue
 secures upper layers
© 2015 Pearson Education, Inc.
Epithelium Characteristics
 Avascular (no blood supply)
 Relies on circulatory system to obtain food and oxygen

Surrounding connective tissues supply via diffusion from
nearby capillaries
 Regenerate easily if well nourished (through normal
cell division)
 Cells on exterior of the skin are exposed to friction and
other hostile substances and are sloughed off
Classification of Epithelia
 Two name system:
 First name = # of layers
 Second name = shape of cells
 Named using number of cell layers:
 Simple—one layer

Absorption/secretion/filtration are main functions
 Stratified—more than one layer

Ideal for protection
 Often found where there is friction or abuse; durable
© 2015 Pearson Education, Inc.
Figure 3.17a Classification and functions of epithelia.
Apical surface
Basal
surface
Simple
Apical surface
Basal
surface Stratified
(a) Classification based on number of cell layers
Epithelial shapes
 Names using shape of cells
 Squamous

Flattened, like fish scales
 Cuboidal

Cube-shaped, like dice
 Columnar

Column-like
© 2015 Pearson Education, Inc.
Figure 3.17b Classification and functions of epithelia.
Squamous
Cuboidal
Columnar
(b) Classification based on cell shape
Figure 3.17c Classification and functions of epithelia.
Number of layers
One layer: simple epithelial
tissues
More than one layer: stratified
epithelial tissues
Squamous
Diffusion and filtration
Secretion in serous membranes
Protection
Cuboidal
Secretion and absorption; ciliated
types propel mucus or
reproductive cells
Secretion and absorption; ciliated
types propel mucus or
reproductive cells
Protection; these tissue types are rare
in humans
Cell shape
Columnar
Transitional
Protection; stretching to accommodate
distension of urinary structures
(c) Function of epithelial tissue related to tissue type
 Remember these general characteristics and you will
be able to classify each type a lot easier !!
Pseudostratified Columnar
 Single layer
 some cells are shorter than others, giving a false
(pseudo) impression of stratification
© 2015 Pearson Education, Inc.
Cilia
Pseudostratified
epithelial
layer
Pseudostratified
epithelial layer
Basement
membrane
Basement
membrane
Connective
tissue
(d) Diagram: Pseudostratified
(ciliated) columnar
Photomicrograph: Pseudostratified
ciliated columnar epithelium lining the
human trachea (560×).
Transitional Epithelium
 Unique because of its ability to become temporarily
modified in arrangement and shape
 modified stratified squamous epithelium
 Can stretch and rebound
 Locations: urinary system organs
© 2015 Pearson Education, Inc.
Figure 3.18f Types of epithelia and their common locations in the body.
Basement
membrane
Transitional
epithelium
Basement
membrane
Transitional
epithelium
Connective
tissue
(f) Diagram: Transitional
Photomicrograph: Transitional epithelium lining of
the bladder, relaxed state (270×); surface rounded cells
flatten and elongate when the bladder fills with urine.
Glandular Epithelium
 Two major gland types:
 Endocrine gland



Ductless; secretions diffuse into blood vessels
All secretions are hormones
Examples include thyroid, adrenals, and pituitary
 Exocrine gland



Secretions empty through ducts to the epithelial surface
Include sweat and oil glands, liver (bile duct), and pancreas
(digestive enzymes), mammary glands (milk)
Includes both internal and external glands
© 2015 Pearson Education, Inc.
Download